A pitot tube or probe is an instrument typically mounted on a vehicle to measure the relative velocity of a fluid in which the vehicle is moving. In one application a pitot probe is mounted on an aircraft to measure relative air velocity during flight. A pitot probe consists of a hollow tube having an open end pointing in the direction of fluid flow or vehicle movement. The hollow tube contains a fluid, which in the case of an aircraft is air, and the pressure within the pitot probe provides the stagnation pressure measurement, which is combined with the static pressure measured elsewhere on the aircraft to arrive at the dynamic pressure, which is used to determine the indicated air speed of the aircraft.
Pitot probes mounted on aircraft commonly have heating elements called pitot heaters to prevent the tube from becoming clogged with ice, which may occur when the aircraft is operating at altitude or otherwise in cold environments. Some heating elements comprise resistive wires that are mounted within the pitot probe and take the form of a coil that heats the tube to prevent ice from forming during flight. Failure of the heating element leads to indicated pitot probe failure, and can cause the pitot tube to become clogged with ice, which will cause an incorrect air speed reading.
Pitot probe service issues can be very costly. Currently, there is no procedure for testing a pitot probe to predict the failure of its heating element. Consequently, pitot probes are routinely replaced on a time interval basis to avoid degradation or failure during use. A disadvantage with such a replacement system is that intact, functioning pitot probes may be discarded even though they are in good working order, resulting in unnecessary material and labor costs.
Accordingly, there is a need for a system and method for testing a pitot probe heating element to determine if is near failure, so that pitot probes are replaced only when needed. Additionally, a system and method for testing a pitot probe heating element to determine if it is near failure would allow the prevention of costly service interruptions due to pitot probe heater failure by allowing the preemptive replacement of a nearly-failed pitot probe.